Hemp concrete mixtures and mortars, preparations method and uses

ABSTRACT

The invention relates to concretes and mortars comprising a hydrophilic component such as hemp, flax or straw; a binder which sets in air through absorption of carbon dioxide after reduction in an aqueous phase; at least one additive which forms a microcapillary system array; and at least one matrix water repellency additive.

CROSS REFERENCE TO RELATED APPLICATION

This application is a 35 USC § 371 National Phase Entry Application fromPCT/FR02/02123, filed Jun. 19, 2002, and designating the U.S.

TECHNICAL FIELD OF THE INVENTION

This invention relates to the technical area of hemp concretes andmortars, that is, ones containing some of the analogue of hemp or hempstalk and/or other components of hemp such as fibers, fibrils, dusts ofhemp and powdered hemp, hereinafter referred to as “components”.

These varieties of mortar and concrete are designed for all BTP(Building and Public Works) applications and to all domestic or othercustomary applications of concretes and mortars.

It is to be noted that a mortar is made up of a mixture of binder suchas lime, cement, or the like and aggregate(s) such as sand, powderedstone, crushed marble, and the like with water. Such a mortar is used inconstruction to bind and/or to cover construction elements.

It is to be noted that concrete is an artificial agglomerate of pebbles,gravel, and sand combined by means of a binder, whether watery or not.

TECHNICAL PROBLEM POSED

Incorporation of derivatives of hemp in a concrete or mortar poses avery serious problem because of the highly hydrophilic nature of the“hemp” component. This component can absorb up to approximately 400percent of its weight of water or water-based liquid, this introducing avery strong reaction competing with the water contained in the mortar orconcrete.

As will be seen later, various techniques have been tried in the priorart to mitigate this serious disadvantage, but no success has beenachieved in preventing the concrete and mortar obtained from exhibitingcharacteristics of drying, setting, and highly uncertain mechanicalproperties. This is not acceptable in such a field, since suchdisadvantages may include setting difficulties in setting, possibly even“broken” setting, failure of the concrete to dry or uncertain drying,and/or bad or uncertain mechanical properties and/or risk of repeatedabsorption of water of external origin (rain water, for example)accompanied by development of microorganisms, mouldinesss,low-temperature embrittlement, etc.

PRIOR ART

Varieties of hemp mortar or concrete in which the hemp component(especially the “tow”) is used as an aggregate, in whole or in part, inpreparations, has been known for a very long time, even since ancienttimes. The array of tools for preparation is universally known as well,as are also the suppliers of current products and the most modernproduct families.

The binders currently used are gypsum, lime (in this instance used ashydraulic binder), and cements, that is, hydraulic binders.

The importance of these products is represented by very good thermal andacoustic insulation combined with very good mechanical strength,including a component of interest from the viewpoint of resistance tocompression and that of elastic return, this making it in fact a verygood product adapted to seismic standards.

These products are used in the form of hemp bricks, paving stones,walls, and more or less light concrete and mortar blocks in all BTP anddomestic applications.

However, they exhibit serious defects which a large part of the industryunder consideration has not succeeded in overcoming, despite all itsefforts. The industry under consideration consequently has adapteditself to well-known yet serious disadvantages such as the drying defectand similar defects.

A significant and recognized need consequently exists for concretes andmortars not marked by these significant, even serious defects or onesprecluding use of such substances while their other excellent propertiesremain.

A particular need exists for renovation or rehabilitation of historicworks and old buildings, an area in which concretes and mortars withhydraulic binder lead to in failures.

SUMMARY OF THE INVENTION

The invention relates to hemp mortars or concretes, that is onesincluding one or more hemp components in their formulation in which thebinder is made up at least in part of what is termed “rich” lime, burntlime in particular.

As is known, rich lime is a binder which sets in air through absorptionof carbon dioxide (CO2) after reduction in an aqueous phase, while theburnt lime is a binder which essentially contains calcium hydroxide,dolomitic lime containing a mixture of calcium hydroxide and magnesiumhydroxide.

The rich lime may be used in various forms such as a paste, a powder,or, in the case of quicklime, in the form of the rock itself.

Use may be made of any desired mixtures of all types and all forms ofrich lime.

The expert may consider and adapt these various combinations as afunction of the specific application contemplated, his generalknowledge, the present description, and optionally simple routine tests.

In one preferred embodiment the binder in question is made up of 20% to90% by weight, preferably 50 to 80% by weight, rich lime and 20% to 40%by weight, preferably 10% to 70% by weight, hydraulic binder such as ahydraulic lime or a cement, and optionally 5% to 10% by weight binderand/or puzzolanic filler(s) of the volcanic ash type, “trass” (which isa volcanic rock well known to the expert), or any other componentpuzzolanic in nature, the total equaling 100%.

Lime exhibits quite significant specific features and constraints incomparison to the customary binders, plasters, and cements which havebeen used for decades.

First of all, particles of lime are very fine ones and result in aspecific Blaine surface much superior to that of hydraulic binders.

It is to be noted, even though this is known to the expert, that thespecific Blaine surface of lime is of the order of 8,000 to 20,000,while that of hydraulic binders is of the order of 2,700 to 5,000.

Next, its setting characteristics are radically different. While cementsand plasters contain silicates, aluminates, and/or sulfates the effectof which in setting is represented by a crystallization phenomenon, theeffect of lime in setting is represented by a carbonation reaction inwhich calcium hydroxide undergoes a series of reductions with water orthe base aqueous fluid of the concrete or mortar. In the case of limewater acts as a simple vector of the necessary CO2.

In addition, its solubility in water is only 1.7 g/l at 10-20° C.

One particular problem associated with use of lime, one which has beenpredictable, because of the difficulty in managing the water of theformulation effectively, as been the difficulty of achieving uniformbehavior and especially good flow properties.

Another prejudice against use of rich lime has been the conception thatrich lime could by definition act in a concrete or mortar only in thevicinity of air, that is, on the surface or at maximum depths of theorder of 1 to 3 cm. The invention now proposes a solution which, againstall expectations, eliminates this problem.

There has also been the legitimate fear of an overly long periodrequired for thorough drying. Refer to FIG. 1A attached, which showsthat this fear has been fully justified.

The invention has overcome these prejudices and has solved the previousproblems as a result of a special formulation which incorporates thespecial and innovative characteristics of porosity and capillarity. Someof the many problems posed, such as caking, had already been solved inthe prior art, but never in the context of use of hemp as a component,which use represents a totally innovative functional approach, as is tobe indicated in what follows.

DETAILED DESCRIPTION OF THE INVENTION

The invention accordingly relates to new formulations for “hemp”concretes and mortars, that is, ones including at least one “component”(in the broad sense indicated in the foregoing) of hemp and/or flaxand/or straw such as rinds of oats or rice and/or generally speaking anycomparable hydrophilic substance, including optionally a syntheticsubstance, individually or in a mixture or mixtures, for the sake ofsimplification referred to in what follows, including the claims, as“hemp” concretes or mortars.

Hence the invention relates to new formulations for “hemp” concretes andmortars, that is, ones including at least one component of hemp asspecified in the foregoing and technically equivalent components whichcomprise the conventional ingredients of mortars and concretes except inthe respect that the binder is made up, in whole or in part, of richlime optionally in various combinations of types and forms of lime asindicated in the foregoing, and in that they also comprise

(a) at least one additive for formation of very fine pores andcapillaries

and

(b) at least one matrix water repellency additive.

The term “matrix water repellency” is to be understood here to mean thatthe mass which encloses the fibers, particles, etc of hemp is subjectedto the water repellent action of the additive.

It is to be noted that the hemp itself is subject to this action, butwithout exerting an effect, since the hemp absorbs the water and is notmade water-repellent because it contains water; on the contrary, afterelimination of the water, the water repellency exerts its effect and thehemp no longer absorbs water, for example, it absorbs neither moisturenor rain water, etc. This is one of the major advantages of theinvention.

The term “formation of very fine pores and capillaries” is used here todesignate formation of a highly complex array whose structure may varyfrom one formulation to the other but which comprises open and/or closedtubular capillaries, as well as closed microbubbles or microspacesand/or closed microcavities, closed tubes among others, arranged,proportioned, and distributed so that the final concrete or mortarexhibits uniform or more or less uniform characteristics and has nosetting or drying defects or uncertain properties, that is, propertiesof arrangement, proportioning, and distribution such that the matrixwater may be evacuated toward the surface during setting and thendrying, while after drying external water (rain) cannot penetrate thenetwork of capillaries.

For the sake of simplification of reading this complex array will bedesignated in what follows, including the claims, as a “microcapillarysystem”.

The expert, who is thoroughly familiar with the problems of setting anddrying of hydraulic concretes and mortars and with the characteristicswhich he must produce in order to formulate a “good” concrete or mortar,and who also is familiar with the difficulties and disadvantages of hempmortars and concretes, will encounter no difficulty in controlling themicrocapillary system claimed for the invention, especially on the basisof the percentage of rich lime, in the light of the followingdescription and examples, and in relying on his personal generalknowledge, and if necessary on a few routine tests, for the purpose ofadaptation to the specific application considered.

In one preferred embodiment the additive for formation of themicrocapillary system comprises one or more plant and/or mineralcolloid.

In another preferred embodiment the additive for formation of themicrocapillary system is suitable for arriving at a capillarity of theorder of 5 to 15 Ångströms, preferably 8 to 10 Ångströms.

In comparison, hemp or flax exhibits a capillarity which is 3 to 5 timesgreater, while a hydraulic binder yields a capillarity of the order ofas much as 10 to 20 times greater.

In another preferred embodiment this additive for formation of themicrocapillary system is suitable for provision of the microcapillarysystem in question with closed tubes and/or masses and/or spaces and/ormicrobubbles and/or microcavities, closed tubes in particular.

While not wishing to be bound to any theory, the Applicant believes thatsuch closed spaces, closed tubes in particular, are capable (optionallywhen combined with open microcapillaries) of extracting the watercontained in the hemp and enabling it to migrate toward the surface inthe form of water as liquid and then water vapor, which ultimately ispropagated to the exterior.

In another, non-restrictive, preferred embodiment the colloids selectedare among the plant colloids such as alginates and/or polysaccharidesand all derivatives of natural or synthetic starches and/orcarragheenates.

Mention may be made in particular of guar hydroxypropyl (polysaccharidefamily), which has yielded the best results.

Good results have also been obtained with the carragheenates (which areproducts similar to alginates) and with calcium alginate.

On the contrary, the alginates of sodium and magnesium have a tendencyto precipitate and are not recommended.

Other microcapillary system formation additives are to be selected fromamong the following:

-   -   etherified galactomannan, and    -   etherified derivatives of guars

and mixtures of these substances.

In one preferred embodiment such water repellency additive comprises atleast one water-repellent agent and one surfactant agent.

While not wishing to be bound to any theory, the Applicant believes thatthe surfactant contributes a “netting” or “mesh” structure whichcontributes greatly to uniformity of the final product and itsproperties.

In one alternative embodiment use is to be made of a surfactant for aneutral or basic medium and/or a surfactant for an acid medium, and/orappropriate mixtures of these substances, as a function of theanticipated evolution of the pH (which any expert is familiar with andcan evaluate).

In one preferred, non-restrictive, embodiment the surfactant orsurfactants selected are among the polysulfonates of calcium, sodium, ormagnesium and in particular among the lignosulfonates.

In another preferred, non-restrictive, embodiment another surfactant orother surfactants to be selected is/are among the following:

-   -   sodium sulfates.

In one preferred embodiment the water-repellent agents selectedpreferably are among the metallic soaps, the maleates, oleates,stearates, and the like of aluminum, magnesium, sodium, lithium, andsimilar salts, and/or siliconates of sodium and mixtures of suchsiliconates.

In one preferred, non-restrictive, embodiment the water-repellentagent(s) selected is/are among the following:

-   -   oleates of sodium.

In one preferred, non-restrictive, embodiment the additives and agentsemployed in accordance with the invention are to be employed in thefollowing proportions.

(a) additive for formation of the microcapillary system:

0.1% to 2% of the total weight of the binder

(b) water-repellent additive:

0.1% to 1% of the total weight of the binder

(c) surfactant

0.002% to 0.2% of the total weight of the binder

A new industrial product is thereby obtained which is characterized inthat it consists of mortars and concretes with a hemp binder componentcomprising rich lime, comprising

(a) at least one additive for formation of very fine pores andcapillaries

and

(b) at least one water repellent additive, and

the setting, mechanical properties, and drying of which are not markedby uncertain behavior.

The invention also relates to a new industrial product of the mortar andconcrete type with a hemp binder component of rich lime, characterizedin that it includes in its mass a microcapillary system which itselfcomprises tubes and/or masses and/or spaces and/or microcavities, inparticular closed tubes capable, especially closed tubes (optionallycombined with open microcapillaries), of extracting water previouslyabsorbed and contained in the hemp and of enabling it to migrate towardthe surface in the form progressively of water and then of water vaporwhich ultimately spreads outward to the point of drying.

This product is also characterized in that its water-repellent matrixrenders the dry fibers of the hemp component water repellent, therebypreventing reabsorption of the water by the hemp component.

In another alternative this product is characterized in that its globalor “residual” thermal conductivity coefficient lambda is of the order of0.8 to 0.12, preferably around 0.1.

It is to be noted by way of comparison that the thermal conductivitycoefficient of a hydraulic concrete or mortar is of the order of 0.6 to1.15, that is, around five to eleven times higher.

Such products would be products used in the BTP (Construction and PublicWorks), ones such as perpends, cutting blocks and blocks of variousshapes, bricks, and the like well known to the expert, for the sake ofsimplification hereinafter referred to as “perpends” as well as slabs,wall linings, floors, ceilings, etc, and the like well known to theexpert.

BRIEF DESCRIPTION OF THE DRAWINGS

Other characteristics and advantages of the invention will be betterunderstood by reading the following description in conjunction with theattached drawing, in which

FIG. 1, which consists of FIGS. 1A (left) and 1B (right) represents aphotograph of two samples (20×30×60 cm) of hemp concrete;

in the figure on the left (1A): concrete not based on the invention(comparative test), made with a mixture of plaster and rich lime (whitearea: excessively long drying time and development of mold fungus)

in the figure on the right (1B): concrete made with a mixture asspecified for the invention

FIG. 2 presents a scanning electron microscope photograph of a limemortar on a hemp granulate (×1,000). The relationship between hemp (A)and hemp (B) is clearly shown. The grains of lime are lodged as far asin the interior of the fiber channels of the plant.

FIG. 3 presents a scanning electron microscope photograph showingbubbles and microbubbles of air and openings of tubular channels in thelime paste (×111). The porosity of the lime paste is represented by airbubbles and tubular channels which have formed after evaporation of themixing water.

FIG. 4 presents a scanning electron microscope photograph showing anetwork of air bubbles and tubular channels (×17). The photograph showswith great clarity the complete envelopment achieved in accordance withthe invention, an amalgam of tubes, closed tubes (some of which arevisible because they are cut off outside the cut), spaces or masses,capillaries, and the hemp cuttings.

FIG. 5 presents a comparable hemp structure WITHOUT the lime component.

Microscopic examination of FIGS. 2 to 5 reveals the presence, as claimedfor the invention, of a significant capillary network made up of airbubbles and tubular channels.

The invention relates to formulations of “hemp” concretes and mortarswith a binder including lime, as well as to new industrial productsconsisting of such mortars and concretes, and also to use as additivesfor “hemp” mortars and concretes of the additive for formation of themicrocapillary system and/or the water repellency additive, as well asproducts made by means of such mortars and concretes or formulation orby means of the additive for formation of the microcapillary systemand/or the water repellency additive, such as bricks, blocks, perpends,various “hemp” elements, and also products for Building and Public Worksor individual structures erected by means of such mortars or concretes,additives or products, such as walls, slabs, covers, linings andcoatings of floors, ceilings, walls, partitions, and similar structures.

The invention also covers all embodiments and all applications whichwill be immediately comprehensible to the expert upon reading thisapplication, on the basis of his own knowledge and optionally simpleroutine tests.

1. A formulation for concretes and mortars, comprising (a) a hydrophiliccomponent selected from the group consisting of hemp, flax and straw;(b) a binder comprising lime which sets in air through absorption ofcarbon dioxide after reduction in an aqueous phase, (c) at least oneadditive which results in the formation of a microcapillary system arraywhich comprises open and/or closed tubular capillaries, closedmicrospaces, closed microcavities and/or closed tubes suitable inarrangement and in proportion and distribution for ensuring that anymatrix water can be evacuated to a surface on setting and then drying,while, after drying, water cannot penetrate said microcapillary systemarray, wherein said additive is selected from the group consisting ofone or more plant colloids, mineral colloids, etherified galactomannan,and etherified derivatives of guars, and (d) at least one matrix waterrepellency additive which prevents said hydrophilic component fromreabsorbing water after drying.
 2. The formulation according to claim 1,wherein the additive which results in the formation of themicrocapillary system array comprises one or more plant and/or mineralcolloids.
 3. The formulation according to claim 1, wherein the additivewhich results in the formation of the microcapillary system arrayresults in a capillarity of the order of 5 to 15 Ångströms.
 4. Theformulation according to claim 3, wherein said capillarity is of theorder of 8 to 10 Ångströms.
 5. The formulation according to claim 2,wherein said additive which results in the formation of themicrocapillary system array results in closed tubes, closed masses,closed spaces, closed microbubbles and/or closed microcavities.
 6. Theformulation according to claim 5, wherein said additive which results inthe formation of the microcapillary system array results in closedtubes.
 7. The formulation according to claim 2, wherein said plantcolloids are selected from the group consisting of alginates,polysaccharides, derivatives of natural starches, derivatives ofsynthetic starches, and carragheenates.
 8. The formulation according toclaim 7, wherein said polysaccharides are colloids of hydroxypropylguar.
 9. The formulation according to claim 7, wherein said plantcolloids are carragheenates in combination with calcium alginate. 10.The formulation according to claim 2, wherein said additive whichresults in the formation of the microcapillary system array is at leastone additive selected from the group consisting of etherifiedgalactomannan and etherified derivatives of guars.
 11. The formulationaccording to claim 1, wherein said matrix water repellency additivecomprises at least one water repellent agent and one surfactant agent.12. The formulation according to claim 11, wherein said surfactant isselected from the group consisting of a surfactant suitable for use in aneutral medium, a surfactant suitable for use in an acid medium, and amixture of surfactants suitable for use in neutral or acid mediums. 13.The formulation according to claim 12, wherein said surfactant is atleast one surfactant selected from the group consisting ofpolysulfonates of calcium, polysulfonates of sodium, polysulfonates ofmagnesium, and lignosulfonates.
 14. The formulation according to claim12, further comprising sodium sulfate.
 15. The formulation according toclaim 1, wherein said matrix water repellency additive is selected fromthe group consisting of metallic soaps; maleates, oleates, and stearatesof aluminum, magnesium, sodium, and/or lithium; siliconates of sodium;and mixtures thereof.
 16. The formulation according to claim 15, whereinsaid matrix water repellency additive is an oleate of sodium.
 17. Theformulation according to claim 11, wherein said additive for theformation of a microcapillary system array is 0.01% to 2% of the totalweight of the binder, said water repellent additive is 0.1% to 1% of thetotal weight of the binder, and said surfactant agent is 0.002% to 0.2%of the total weight of the binder.
 18. The formulation according toclaim 1, wherein said lime is burnt lime which comprises calciumhydroxide and magnesium hydroxide.
 19. The formulation according toclaim 1, wherein said binder comprises 20-90% by weight lime and 10-70%by weight hydraulic binder.
 20. The formulation according to claim 19,further comprising 5-10% by weight of a puzzolanic component.
 21. Theformulation according to claim 1, wherein said binder comprises 50-80%by weight lime and 20-40% by weight hydraulic binder.
 22. An industrialproduct comprising concrete and/or mortar, wherein said concrete ormortar comprises (a) a hydrophilic component selected from the groupconsisting of hemp, flax and straw; (b) a binder comprising lime whichsets in air through absorption of carbon dioxide after reduction in anaqueous phase, (c) at least one additive which results in the formationof a microcapillary system array which comprises open and/or closedtubular capillaries, closed microspaces, closed microcavities and/orclosed tubes suitable in arrangement and in proportion and distributionfor ensuring that any matrix water can be evacuated to a surface onsetting and then drying, while, after drying, water cannot penetratesaid microcapillary system array, wherein said additive is selected fromthe group consisting of one or more plant colloids, mineral colloids,etherified galactomannan, and etherified derivatives of guars, and (d)at least one matrix water repellency additive which prevents saidhydrophilic component from reabsorbing water after drying.
 23. Theindustrial product according to claim 22, wherein said product has athermal conductivity coefficient lambda of the order of 0.08 to 0.12.24. The industrial product according to claim 23, wherein said thermalconductivity coefficient lambda is around 0.1.
 25. A method for makingbricks, blocks, perpends, wall elements, slabs, linings, covers,coatings for floors, ceilings, walls, partitions, or individualstructures, comprising preparing concrete and/or mortar which comprises(a) a hydrophilic component selected from the group consisting of hemp,flax and straw; (b) a binder comprising lime which sets in air throughabsorption of carbon dioxide after reduction in an aqueous phase, (c) atleast one additive which results in the formation of a microcapillarysystem array which comprises open and/or closed tubular capillaries,closed microspaces, closed microcavities and/or closed tubes suitable inarrangement and in proportion and distribution for ensuring that anymatrix water can be evacuated to a surface on setting and then drying,while, after drying, water cannot penetrate said microcapillary systemarray, wherein said additive is selected from the group consisting ofone or more plant colloids, mineral colloids, etherified galactomannan,and etherified derivatives of guars, and (d) at least one matrix waterrepellency additive which prevents said hydrophilic component fromreabsorbing water after drying, and forming said concrete and/or mortarinto bricks, blocks, perpends, wall elements, slabs, linings, covers,coatings for floors, ceilings, walls, partitions, or individualstructures.